Electric vehicles such as electric wheelchairs include those having a drive device for driving each of left and right drive wheels individually with a motor. The motor is mounted on the vehicle body and delivers torque to the axle of the drive wheel to rotate the drive wheel. See, for example, JP1997-296829A and JP2000-70309A.
To give a reduced thickness to the drive device, it is required to enlarge the drive device diametrically of the drive wheel, and it is consequently impossible to diminish the drive wheel in diameter. An increase in the diameter of the drive wheel entails the problem that greater motor torque acts on the drive wheel under the same load. In the case of electric wheelchairs, furthermore, the increase in the diameter of the drive wheel gives rise to the problem that the drive wheel is liable to become an obstacle when the wheelchair is driven indoors, or when the user moves from the wheel chair to the bed or from the bed to the wheelchair.
With the drive devices disclosed in the above publications and having a reduced thickness, the motor and the electromagnetic brake are dynamically cut off from the drive wheel when the clutch mechanism is disengaged. If the clutch mechanism is disengaged, for example, on a downward slope in error, the dynamic braking force of the motor and the braking force of the brake fail to act on the drive wheel, possibly permitting the wheelchair to run down the downward slope as accelerated.